U.S. patent application number 15/546946 was filed with the patent office on 2018-01-18 for impact tool.
The applicant listed for this patent is HITACHI KOKI CO., LTD.. Invention is credited to Satoshi ABE, Kuniaki KANBE.
Application Number | 20180015603 15/546946 |
Document ID | / |
Family ID | 56543079 |
Filed Date | 2018-01-18 |
United States Patent
Application |
20180015603 |
Kind Code |
A1 |
ABE; Satoshi ; et
al. |
January 18, 2018 |
IMPACT TOOL
Abstract
An impact tool in which stop control of a motor as power source
of a tool bit is changed in accordance with a predetermined
condition is provided. A hammer drill having two or more operating
modes including a hammer mode in which an impact force is
transmitted to a tool bit whereas a rotational force s not
transmitted thereto and a hammer drill mode in which at least the
rotational force is transmitted to the tool bit includes a motor as
a power source and a control part that performs stop control to
stop the motor, and the control part performs any one of two or
more of the stop controls in accordance with a predetermined
condition.
Inventors: |
ABE; Satoshi; (Ibaraki,
JP) ; KANBE; Kuniaki; (Ibaraki, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HITACHI KOKI CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
56543079 |
Appl. No.: |
15/546946 |
Filed: |
January 8, 2016 |
PCT Filed: |
January 8, 2016 |
PCT NO: |
PCT/JP2016/050499 |
371 Date: |
July 27, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B25D 2216/0015 20130101;
B25D 2250/121 20130101; H02P 3/22 20130101; B25D 2216/0084
20130101; B25D 2250/221 20130101; B25D 2250/261 20130101; B25D
2216/0023 20130101; B25D 17/24 20130101; H02P 3/12 20130101; B25D
16/006 20130101; H02P 3/08 20130101 |
International
Class: |
B25D 16/00 20060101
B25D016/00; B25D 17/24 20060101 B25D017/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 2015 |
JP |
2015-014474 |
Claims
1. An impact tool having two or more operating modes including a
first operating mode in which an impact force is transmitted to a
tool bit whereas a rotational force is not transmitted to the tool
bit and a second operating mode in which at least the rotational
force is transmitted to the tool bit, the impact tool comprising: a
motor as a power source; and a control part that performs stop
control to stop the motor, wherein the control part performs any
one of two or more of the stop controls in accordance with a
predetermined condition.
2. The impact tool according to claim 1, wherein the stop controls
include stop control having a large braking force to the motor, and
stop control having a small braking force to the motor.
3. The impact tool according to claim 2, wherein the stop control
having the large braking force is an active-stop control including
a braking process to actively stop rotation of the motor, and the
stop control having the small braking force is a natural-stop
control including no braking process.
4. The impact tool according to claim 2, wherein the control part
performs the stop control having the small braking force when the
first operating mode is selected, arid performs the stop control
having the large braking force when the second operating mode is
selected.
5. The impact tool according to claim 2, wherein the control part
performs the stop control having the large braking force when the
operating mode is switched during rotation of the motor.
6. The impact tool according to claim 4, further comprising a mode
detection part that transmits a mode detection signal indicating a
selected operating mode to the control part.
7. The impact tool according to claim 2, wherein the motor is a
brushless motor having a stator provided with a plurality of coils
and a rotor provided with magnets with different polarities, the
control part controls a plurality of switching elements that
control power supply to the plurality of coils, the control part
controls the switching elements so that the power supply to the
coils is cut off in the stop control having the small braking
force, and the control part controls the switching elements so that
a closed circuit including the coils is formed and a regenerative
brake acts on the rotor in the stop control having the large
braking force.
Description
TECHNICAL FIELD
[0001] The present invention relates to an impact tool that applies
a rotational force or an impact force to a tool bit to drill a hole
in an object or crush an object with the tool bit.
BACKGROUND ART
[0002] An impact tool that applies a rotational force or an impact
force to a tool bit such as a drill bit to drill a hole in a
concrete wall, a concrete floor or the like or crush it with the
drill bit has been known, and such an impact tool is generally
referred to as a "hammer drill".
[0003] Most of conventional hammer drills have at least two
operating modes. A conventional hammer drill has, for example, a
hammer mode in which only an impact force is transmitted to a drill
bit, and a hammer drill mode in which both of an impact force and a
rotational force are transmitted to the drill bit. In the
conventional hammer drill having a plurality of operating modes,
when a trigger lever is operated by an operator, required power is
transmitted to the drill bit in accordance with a selected
operating mode.
RELATED ART DOCUMENTS
Patent Documents
[0004] Patent Document 1: Japanese Patent No. 4281273
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0005] For the work using the impact tool, it is sometimes
preferable that movement of a tool bit is stopped instantaneously.
For example, when the hammer mode is selected to crush an object,
it is preferable to minimize a time lag between an operation of a
trigger lever by a worker and a start of the drill bit and between
a release of operation of the trigger lever and a stop of the drill
bit. In addition, in a hammer drill having a plurality of operating
modes, it is preferable that power transmission to the drill bit is
stopped immediately when the operating mode is switched at an
unexpected timing.
[0006] An object of the present invention is to provide an impact
tool in which stop control of a motor as a power source of a tool
bit is changed in accordance with a predetermined condition.
Means for Solving the Problems
[0007] In an aspect of the present invention, an impact tool has
two or more operating modes including a first operating mode in
which an impact force is transmitted to a tool bit whereas a
rotational force is not transmitted to the tool bit and a second
operating mode in which at least the rotational force is
transmitted to the tool bit. The impact tool includes: a motor as a
power source; and a control part that performs stop control to stop
the motor, and the control part performs any one of two or more of
the stop controls in accordance with a predetermined condition.
[0008] In another aspect of the present invention, the stop
controls include stop control having a large braking force to the
motor, and stop control having a small braking force to the
motor.
[0009] In another aspect of the present invention, the stop control
having the large braking force is an active-stop control including
a braking process to actively stop rotation of the motor, and the
stop control having the small braking force is a natural-stop
control including no braking process.
[0010] In another aspect of the present invention, the control part
performs the stop control having the small braking force when the
first operating mode is selected, and performs the stop control
having the large braking force when the second operating mode is
selected.
[0011] In another aspect of the present invention, the control part
performs the stop control having the large braking force when the
operating mode is switched during rotation of the motor.
[0012] In another aspect of the present invention, the impact tool
further includes a mode detection part that transmits a mode
detection signal indicating a selected operating mode to the
control part.
[0013] In another aspect of the present invention, the motor is a
brushless motor having a stator provided with a plurality of coils
and a rotor provided with magnets with different polarities. In
this aspect, the control part controls a plurality of switching
elements that control power supply to the plurality of coils. In
addition, the control part controls the switching elements so that
the power supply to the coils is cut off in the stop control having
the small braking force. Also, the control part controls the
switching elements so that a closed circuit including the coils is
formed and a regenerative brake acts on the rotor in the stop
control having the large braking force.
Effects of the Invention
[0014] According to the present invention, it is possible to
realize an impact tool in which stop control of a motor as a power
source of a tool bit is changed in accordance with a predetermined
condition.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0015] FIG. 1 is a cross-sectional view showing a structure of
hammer drill;
[0016] FIG. 2 is another cross-sectional view showing the structure
of the hammer drill;
[0017] FIG. 3 is a block diagram showing various circuits provided
in the hammer drill;
[0018] FIG. 4 is a flowchart showing one example of ON/OFF control
of a brushless motor; and
[0019] FIG. 5 is a flowchart showing another example of the ON/OFF
control of the brushless motor.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] Hereinafter, a first embodiment of an impact tool according
to the present invention will be described. The impact tool
according to the present embodiment is a hammer drill capable of
attaching and detaching a drill bit as an example of a tool bit.
Although applications of the hammer drill according to the present
embodiment are not particularly limited, the hammer drill is
suitable for the work for drilling a hole in an object such as a
concrete wall or a stone material or for crushing the object. In
addition, the hammer drill according to the present embodiment has
a first operating mode in which an impact force is transmitted to
the drill bit whereas a rotational force is not transmitted
thereto, and a second operating mode in which at least the
rotational force is transmitted to the drill bit. Further, in the
second operating mode in this embodiment, the impact force is
transmitted to the drill bit in addition to the rotational force.
Accordingly, in the following description, the first operating mode
is referred to as a "hammer mode", and the second operating mode is
referred to as a "hammer drill mode".
[0021] As shown in FIG. 1, the hammer drill 1 includes a cylinder
housing 2, an intermediate housing 3, a motor housing 4, and a
handle 5, and these are fixed to and integrated with each other.
The cylinder housing 2 is cylindrical as a whole, and the
intermediate housing 3 and the motor housing 4 are arranged between
a first longitudinal end (rear end) of the cylinder housing 2 and
the handle 5. The intermediate housing 3 and the motor housing 4
are vertically overlapped, and one end (lower end) of the handle 5
is coupled to the motor housing 4, and the other end (upper end) of
the handle 5 is coupled to the intermediate housing 3. The handle 5
is coupled to the intermediate housing 3 and the motor housing 4
with vibration-isolation mechanism interposed therebetween.
[0022] Inside the cylinder housing 2, a cylinder 10 in a
cylindrical shape and a retainer sleeve 11 are housed. The cylinder
10 and the retainer sleeve 11 are concentric, and a part of the
retainer sleeve 11 protrudes from a tip of the cylinder housing 2.
The cylinder 10 and the retainer sleeve 11 are engaged so as to be
relatively unrotatable, and the cylinder 10 and the retainer sleeve
11 integrally rotate about a center axis as a rotation axis when a
rotational force is transmitted to the cylinder 10. In addition, a
part of the drill bit (not shown) is inserted into the retainer
sleeve 11. The drill bit inserted into the retainer sleeve 11 is
engaged with the retainer sleeve 11 so as to be unmovable in a
rotational direction and movable within a predetermined range in an
axial direction. Consequently, when the cylinder 10 and the
retainer sleeve 11 rotate, a rotational force is transmitted to the
drill bit, and the drill bit is rotated. Further, when an impact
force is transmitted to the drill bit, the drill bit is
reciprocally moved within a predetermined range in the axial
direction. Movement of the cylinder 10, the retainer sleeve 11, and
the drill bit will be described in detail later.
[0023] Inside the cylinder 10, a piston 20 and an impact element 21
are housed in a reciprocally movable manner. In addition, an
intermediate element 22 is housed in a reciprocally movable manner
so as to be laid across the cylinder 10 and the retainer sleeve 11.
The piston 20, the impact element 21, and the intermediate element
22 are aligned in this order from a rear side to a front side of
the cylinder 10. Further, an air chamber 23 is provided between the
piston 20 and the impact element 21 inside the cylinder 10.
[0024] A motor 30 as a power source is housed in the motor housing
4. The motor 30 is an inner rotor brushless motor, and has a stator
31 in a cylindrical shape, a rotor 32 disposed inside the stator
31, and an output shaft 33 disposed inside the rotor 32. The output
shaft 33 is fixed to the rotor 32, and vertically extends to pass
through the rotor 32. A center axis of the output shaft 33 is
orthogonal to a center axis of the cylinder 10 and the retainer
sleeve 11.
[0025] An upper part of the output shaft 33 protruding from the
rotor 32 passes through a partition between the motor housing 4 and
the intermediate housing 3, to enter inside the intermediate
housing 3. A pinion gear 34 is provided at an upper end of the
output shaft 33 protruding inside the intermediate housing 3.
Inside the intermediate housing 3, a first driving shaft 40 is
rotatably disposed near the output shaft 33, and a second driving
shaft 50 rotatably disposed near the first driving shaft 40. The
output shaft 33, the first driving shaft 40, and the second driving
shaft 50 are in parallel with each other.
[0026] A first gear 41 that is meshed with the pinion gear 34 is
provided at a lower part of the first driving shaft 40, an
eccentric pin 42 is provided at an upper part of the first driving
shaft 40, and this eccentric pin 42 is coupled to the piston 20 via
a connecting rod 43.
[0027] A second gear 51 that is meshed with the first gear 41 is
provided at a lower part of the second driving shaft 50, a bevel
gear 52 is provided at an upper part of the second driving shaft
50, and this bevel gear 52 is meshed with a ring gear 53 disposed
around the cylinder. The ring gear 53 is mounted on an outer
circumferential surface of the cylinder 10 via a sliding bearing
(metal), and freely rotates with respect to the cylinder 10.
[0028] A sleeve 54 is provided on the outer circumferential surface
of the cylinder 10 in addition to the ring gear 53. The sleeve 54
integrally rotates with the cylinder 10, and individually slides
reciprocally in an axial direction of the cylinder 10. A spring
always applies a force to the sleeve 54 in a direction approaching
to the ring gear 53.
[0029] A mode-switching dial 60 is provided on a top surface of the
intermediate housing 3. The hammer mode and the hammer drill mode
are switched by a rotational operation of the mode-switching dial
60. In other words, a power transmission path in which only an
impact force is transmitted to the drill bit and a power
transmission path in which an impact force and a rotational force
are transmitted to the drill bit are selectively formed by the
rotational operation of the mode-switching dial 60. The power
transmission path will be described in detail later.
[0030] When the mode-switching dial 60 shown in FIG. 1 is rotated
by 180 degrees in a first direction, an operation arm 61 moves
forward in the axial direction of the cylinder 10 as shown in FIG.
2. Then, the operation arm 61 moving forward pushes the sleeve 54,
and the sleeve 54 slides forward against the force of the spring.
As a result, engagement of the ring gear 53 and the sleeve 54 is
released. When the ring gear 53 and the sleeve 54 are thus
disengaged, transmission of the rotational force to the cylinder 10
is cut off.
[0031] On the other hand, when the mode-switching dial 60 shown in
FIG. 2 is rotated by 180 degrees in a second direction, the
operation arm 61 moves backward as shown in FIG. 1. Then, contact
of the operation arm 61 and the sleeve 54 is released, and the
sleeve 54 slides backward by the force of the spring. As a result,
the ring gear 53 and the sleeve 54 are engaged with each other.
When the ring gear 53 and the sleeve 54 are thus engaged, the
rotational force is transmitted to the cylinder 10.
[0032] As shown in FIGS. 1 and 2, the handle 5 has a trigger lever
70 as a first operation part that is operated by an operator, and
an ON-lock button 80 as a second operation part that is operated by
the operator. In addition, a main switch 71 that is turned on/off
based on the operation of the trigger lever 70 is provided inside
the handle 5. The ON-lock button 80 contains a lighting part (LED
in this embodiment) that is lighted and extinguished in accordance
with a predetermined condition. Further, an operation panel 90
including a rotation-number setting button and a plurality of LEDs
is also provided in the handle 5. When the rotation-number setting
button on the operation panel 90 is pressed, a target rotation
number of the brushless motor 30 is switched stepwise in accordance
with the number of presses. In addition, the number of lighted LEDs
is changed in accordance with the set target rotation number so as
to notify the set target rotation number.
[0033] Next, the power transmission path in the hammer drill 1 will
be described. When the brushless motor 30 shown in FIGS. 1 and 2 is
actuated, rotation of the output shaft 33 is transmitted to the
first driving shaft 40 via the pinion gear 34 and the first gear
41, and the first driving shaft 40 is rotated. In addition, the
rotation of the output shaft 33 is transmitted to the second
driving shaft 50 via the pinion gear 34, the first gear 41, and the
second gear 51, and the second driving shaft 50 is rotated.
[0034] When the first driving shaft 40 rotates, the eccentric pin
42 provided at the upper end of the first driving shaft 40 is
rotated about a center axis of the first driving shaft 40 as a
rotation axis. Namely, the eccentric pin 42 revolves around the
center axis of the first driving shaft 40. Consequently, the piston
20 coupled to the eccentric pin 42 via the connecting rod 43 is
reciprocally moved in the cylinder 10. When the piston 20 moves in
a direction separating from the impact element 21, namely, when the
piston 20 moves backward, pressure in the air chamber 23 is
decreased, and the impact element 21 moves backward. On the other
hand, when the piston 20 moves in a direction approaching to the
impact element 21, namely, when the piston 20 moves forward, the
pressure in the air chamber 23 is increased, and the impact element
21 moves forward. When the impact element 21 moves forward, the
impact element 21 impacts the intermediate element 22, and the
intermediate element impacts the drill bit (not shown). The impact
force is intermittently transmitted to the drill bit in this
manner.
[0035] When the second driving shaft 50 rotates, the bevel gear 52
provided at an upper end of the second driving shaft 50 is rotated,
and the ring gear 53 meshed with the bevel gear 52 is rotated. At
this time, when the hammer mode is selected by the rotational
operation of the mode-switching dial 60, namely, when engagement of
the ring gear 53 and the sleeve 54 is released as shown in FIG. 2,
rotation of the ring gear 53 is not transmitted to the cylinder 10,
and the ring gear 53 idly rotated on the cylinder 10. Consequently,
the rotational force is not transmitted to the drill bit, and only
the impact force is transmitted thereto.
[0036] On the other hand, when the hammer drill mode is selected by
the rotational operation of the mode-switching dial 60, namely,
when the ring gear 53 and the sleeve 54 are engaged as shown in
FIG. 1, the rotation of the ring gear 53 is transmitted to the
cylinder 10 via the sleeve 54, and the cylinder 10 and the retainer
sleeve 11 are integrally rotated. Accordingly, the impact force is
intermittently transmitted to the drill bit held by the retainer
sleeve 11, and the rotational force is continuously transmitted
thereto.
[0037] Next, various circuits provided in the hammer drill 1
according to the present embodiment and a circuit configuration or
the like of the brushless motor 30 will be described with reference
to FIG. 3. As shown in FIGS. 1 and 2, a control board 100 is
provided between the brushless motor 30 and the handle 5. As shown
in FIG. 3, the brushless motor 30, the main switch 71, the ON-lock
button 80, the operation panel 90 and the like described above are
electrically connected to the control board 100. In addition, a
switching circuit 102, a rectifier circuit 103, a power factor
improvement circuit 104, and a motor control unit 105 including a
controller 106 and the like described later are mounted on the
control board 100.
[0038] As shown in FIG. 3, the stator 31 of the brushless motor 30
(FIGS. 1 and 2) includes coils U1, V1, and W1 corresponding to
U-phase, V-phase, and W-phase. On the other hand, four permanent
magnets of two types with different polarities are provided in the
rotor 32 (FIGS. 1 and 2) of the brushless motor 30. These four
permanent magnets are disposed along a rotational direction of the
rotor 32 at equal intervals. As shown in FIG. 3, three magnetic
sensors S1, S2, and S3 are disposed near the rotor 32. These
magnetic sensors S1, S2, and S3 detect variation in magnetic force
attendant on the rotation of the rotor 32, and output an electric
signal to a rotor-position detection circuit 101. Hall elements are
used for the magnetic sensors S1, S2, and S3 in this
embodiment.
[0039] The switching circuit 102 shown in FIG. 3 controls power
supply to the coils U1, V1, and W1 of the stator 31. The rectifier
circuit 103 that converts AC current to DC current and the power
factor improvement circuit 104 that boosts a voltage of the DC
current output from the rectifier circuit 103 and supplies it to
the switching circuit 102 are disposed before the switching circuit
102. The rectifier circuit 103 is a bridge circuit in which four
diode elements are connected with each other. The power factor
improvement circuit 104 has a field effect transistor, an
integrated circuit that outputs a pulse width modulation (PWM)
control signal to the field effect transistor, and a capacitor, and
suppresses a high frequency current generated in the switching
circuit 102 to a limit value or less.
[0040] The switching circuit 102 is a 3-phase full-bridge inverter
circuit, and has two switching elements Tr1 and Tr2 connected in
parallel, two switching elements Tr3 and Tr4 connected in parallel,
and two switching elements Tr5 and Tr6 connected in parallel. Each
of the switching elements is an IGBT (Insulated Gate Bipolar
Transistor). The switching elements Tr1 and Tr2 are connected to
the coil U1 to control current supplied to the coil U1. The
switching elements Tr3 and Tr4 are connected to the coil V1 to
control current supplied to the coil V1. The switching elements Tr5
and Tr6 are connected to the coil W1 to control current supplied to
the coil W1.
[0041] The switching elements Tr1, Tr3, and Tr5 are connected to a
positive-electrode-side output terminal of the power factor
improvement circuit 104, and the switching elements Tr2, Tr4, and
Tr6 are connected to a negative-electrode-side output terminal of
the power factor improvement circuit 104. Namely, the switching
elements Tr1, Tr3, and Tr5 are on a high side, and the switching
elements Tr2, Tr4, and Tr6 are on a low side.
[0042] In this embodiment, the coils U1, V1, and W1 are
star-connected. However, a connection method of the coils U1, V1,
and W1 is not limited to the star connection, and it may be, for
example, a delta connection.
[0043] The motor control unit 105 shown in FIG. 3 includes the
controller 106 as a control part, a control-signal output circuit
107, the rotor-position detection circuit 101, and a
motor-rotation-number detection circuit 108. The controller 106
computes and outputs a signal for controlling the brushless motor
30. The control signal output from the controller 106 is input to
the switching circuit 102 through the control-signal output circuit
107. The rotor-position detection circuit 101 detects a rotational
position of the rotor 32 (FIGS. 1 and 2) based on the electric
signal output from the magnetic sensors S1, S2, and S3, and outputs
a signal indicating the rotational position of the rotor 32. The
position detection signal output from the rotor-position detection
circuit 101 is input to the controller 106 and the
motor-rotation-number detection circuit 108. The
motor-rotation-number detection circuit 108 detects the rotation
number of the rotor 32, namely, the motor rotation number, and
outputs a signal indicating the motor rotation number. The
rotation-number detection signal output from the
motor-rotation-number detection circuit 108 is input to the
controller 106. The controller 106 performs feedback control based
on the rotation-number detection signal so that the motor rotation
number is maintained at the target rotation number.
[0044] An ON signal and an OFF signal which are output from the
main switch 71 by the operation of the trigger lever 70 shown in
FIGS. 1 and 2 are input to the controller 106 shown in FIG. 3. When
the trigger lever 70 shown in FIGS. 1 and 2 is operated by an
operator, the main switch 71 outputs the ON signal or the OFF
signal in accordance with the operation. To be specific, the ON
signal is output from the main switch 71 when the trigger lever 70
is pulled, and the OFF signal is output from the main switch 71 or
the output of the ON signal is stopped when the pulling of the
trigger lever 70 is released. When the controller 106 receives the
ON signal output from the main switch 71, it determines that the
main switch 71 is turned on. On the other hand, when the controller
106 receives the OFF signal output from the main switch 71 or when
the reception of the ON signal ceases, the controller 106
determines that the main switch 71 is turned off.
[0045] An ON-lock signal output from the ON-lock button 80 shown in
FIGS. 1 and 2 is input to the controller 106 shown in FIG. 3. The
ON-lock button 80 in this embodiment is a tactile switch that
outputs (transmits) a signal for each operation. Accordingly, the
ON-lock signal is input to the controller 106 shown in FIG. 3 every
time when the ON-lock button 80 is operated. In other words, the
controller 106 receives the ON-lock signal every time when the
ON-lock button 80 is pressed.
[0046] Referring back to FIGS. 1 and 2, a sensor 62 as a mode
detection part is provided in the intermediate housing 3. This
sensor 62 outputs (transmits) an electric signal (mode detection
signal) when the mode-switching dial 60 is rotationally operated to
a predetermined position. The mode detection signal output from the
sensor 62 is input to the controller 106 shown in FIG. 3. The
mode-switching dial 60 shown in FIGS. 1 and 2 contains a permanent
magnet 60a. When the mode-switching dial 60 is rotationally
operated to a position shown in FIG. 2, namely, when the hammer
mode is selected, the permanent magnet 60a contained in the
mode-switching dial 60 is positioned near the sensor 62 (right
above the sensor 62 in this embodiment). Then, the sensor 62
detects a magnetic force of the permanent magnet 60a, and the
sensor 62 outputs the mode detection signal. On the other hand,
when the mode-switching dial 60 is rotationally operated to a
position shown in FIG. 1, namely, when the hammer drill mode is
selected, the permanent magnet 60a contained in the mode-switching
dial 60 is separated from the sensor 62. Then, the sensor 62 does
not detect the magnetic force of the permanent magnet 60a, and the
output of the mode detection signal from the sensor 62 ceases.
Consequently, the controller 106 shown in FIG. 3 can determine
whether the selected operating mode is the hammer mode or not
depending on presence or absence of the input of the mode detection
signal.
[0047] (First Control Flow) Next, one example of control of the
brushless motor 30 (ON/OFF control) which is performed by the
controller 106 shown in FIG. 3 will be described mainly with
reference to FIGS. 3 and 4. Note that the brushless motor 30 is
abbreviated to a "motor 30" in the following description.
[0048] When a power cable is connected to a power source, control
by the controller 106 is started. The controller 106 firstly
determines whether the selected operating mode is the hammer mode
or not (S1). When the operating mode is the hammer mode (S1: Yes),
the controller 105 determines whether the main switch 71 is turned
on or not (S2). Namely, the controller 106 determines whether the
trigger lever 70 (FIGS. 1 and 2) is pulled or not. When the main
switch 71 is turned on (S2: Yes), the controller 106 turns on the
motor 30 (S3). Thereafter, the controller 106 repeats the steps S1
to S3 to maintain the operating state of the motor 30. However, if
the main switch 71 is turned off during the repetition of the steps
S1 to S3 (S2: No), the controller 106 performs a natural-stop
control. To be specific, the controller 106 turns off the motor
(S4). More specifically, the controller 105 turns off the switching
elements Tr1, Tr2, Tr3, Tr4, Tr5, and Tr6, and cuts off the power
supply to the coils V1, U1, and W1 provided in the stator 31.
[0049] As described above, when the selected operating mode is the
hammer mode, the motor 30 is started up by the operation of the
trigger lever 70 shown in FIGS. 1 and 2. Further, ON/OFF of the
motor 30 is controlled based on the operation of the trigger lever
70. Furthermore, when the operation of the trigger lever 70 is
released, the motor 30 is stopped by the natural-stop control
including no braking process. Consequently, even when the trigger
lever 70 is operated again immediately after the operation of the
trigger lever 70 is released, the rotation number of the motor 30
smoothly rises.
[0050] On the other hand, when the selected operating mode is the
hammer drill mode (S1: No), the controller 106 determines whether
the main switch 71 is turned on or not (S5). Namely, the controller
106 determines whether the trigger lever 70 (FIGS. 1 and 2) is
pulled or not. When the main switch 71 is turned on (S5: Yes), the
controller 106 turns on the motor 30 (S6). Thereafter, the
controller 106 repeats the steps S1, S5, and S6 to maintain the
operating state of the motor 30. However, if the main switch 71 is
turned off during the repetition of the steps S1, S5, and S6 (S5:
No), the controller 106 performs an active-stop control. To be
specific, the controller 106 turns off the motor 30, and also
applies a brake to the motor 30 (S7). More specifically, the
controller 106 selectively turns on/off the switching elements Tr1,
Tr2, Tr3, Tr4, Tr5, and Tr6, and forms a closed circuit including
at least one of the coils V1, U1, and W1 provided in the stator 31.
Consequently, when the rotor 32 (FIGS. 1 and 2) rotates, a
regenerative brake acts on the rotor 32. Thus, the active-stop
control includes a braking process for actively stopping the
rotation of the motor 30 (rotor 32).
[0051] As described above, when the selected operating mode is the
hammer drill mode, the motor 30 is started up by the operation of
the trigger lever 70 shown in FIGS. 1 and 2. Further, ON/OFF of the
motor 30 is controlled based on the operation of the trigger lever
70. Furthermore, when the operation of the trigger lever 70 is
released, the motor 30 is stopped by the active-stop control
including the braking process. Accordingly, it is possible to
prevent the motor 30 from continuously rotating by inertia, or
suppress the time of the rotation by inertia to an extremely short
time, after the operation of the trigger lever 70 is released. Note
that, when the operation of the trigger lever (FIGS. 1 and 2) is
released in the hammer mode, the motor 30 is stopped by the
natural-stop control including no braking process as described
above. Namely, the stop control performed by the controller 106
includes at least two stop controls (active-stop control and
natural-stop control) with different braking forces to the motor
30, and the controller 106 performs either of these two stop
controls in accordance with a predetermined condition.
[0052] (Second Control Flow) Next, another example of control of
the brushless motor 30 (ON/OFF control) which is performed by the
controller 106 shown in FIG. 3 will be described mainly with
reference to FIGS. 3 and 5.
[0053] When a power cable is connected to a power source, control
by the controller 106 is started. The controller 106 firstly
determines whether the selected operating mode is the hammer mode
or not (S1) When the operating mode is not the hammer mode (S1:
No), the controller 106 determines whether the main switch 71 is
turned on or not (S2). Namely, the controller 106 determines
whether the trigger lever 70 (FIGS. 1 and 2) is pulled or not. When
the main switch 71 is turned on (S2: Yes), the controller 106 turns
on the motor 30 (S3). Thereafter, the controller 106 repeats the
steps S1 to S3 to maintain the operating state of the motor 30.
However, if the main switch 71 is turned off during the repetition
of the steps S1 to S3 (S2: No), the controller 106 performs the
active-stop control.
[0054] As described above, when the selected operating mode is the
hammer drill mode, the motor 30 is started up by the operation of
the trigger lever 70 shown in FIGS. 1 and 2. In addition, ON/OFF of
the motor 30 is controlled based on the operation of the trigger
lever 70. Further, when the operation of the trigger lever 70 is
released, the motor 30 is stopped by the active-stop control
including the braking process. Accordingly, it is possible to
prevent the motor 30 from continuously rotating by inertia, or
suppress the time of the rotation by inertia to an extremely short
time, after the operation of the trigger lever 70 is released.
[0055] On the other hand, when the selected operating mode is the
hammer mode (S1: Yes), the controller 106 determines the presence
or absence of the reception of the ON-lock signal (S5). Namely, the
controller 106 determines whether the ON-lock button 80 (FIGS. 1
and 2) is pressed or not. When the controller 106 receives the
ON-lock signal (S5: Yes) the controller 106 lights the LED
contained in the ON-lock button 80 (S6) and turns on the motor 30
(S7).
[0056] Next, the controller 106 determines whether the main switch
71 is turned on or not (S8). Namely, the controller 106 determines
whether the trigger lever 70 (FIGS. 1 and 2) is pulled or not. When
the main switch 71 is not turned on (S8: No), the controller 106
determines the presence or absence of the reception of the ON-lock
signal (S9). When the controller 106 does not receive the ON-lock
signal (S9: No), the controller 106 determines the presence or
absence of the reception of the mode detection signal (S10).
Namely, the controller 106 determines the presence or absence of
the operation of the mode-switching dial 60 (FIGS. 1 and 2). When
it is determined that the mode detection signal is received and the
mode is not switched (S10: No), the controller 106 returns to the
step S8. Thereafter, the controller 106 repeats the steps S8 to S10
to maintain the motor 30 in the operating state. In other words,
the controller 106 performs the ON-lock control to maintain the
motor 30 in the operating state even when the trigger lever 70
(FIGS. 1 and 2) is not operated.
[0057] However, when it is determined that the mode detection
signal is not received and the mode is switched (S10: Yes) while
the ON-lock control is performed (during the repetition of the
steps S8 to S10), the controller 106 extinguishes the LED contained
in the ON-lock button 80 (S11), and performs the active-stop
control (S12). Namely, when the operating mode is switched while
the ON-lock control is performed, the motor 30 is stopped by the
active-stop control including the braking process.
[0058] Moreover, when the main switch 71 is turned on (S8: Yes) or
the ON-lock signal is received (S9: Yes) while the ON-lock control
is performed (during the repetition of the steps S8 to S10), the
controller 106 extinguishes the LED contained in the ON-lock button
80 (S13), and performs the natural-stop control. Namely, when the
trigger lever 70 (FIGS. 1 and 2) is pulled or the ON-lock button 80
(FIGS. 1 and 2) is pressed while the ON-lock control is performed,
the motor 30 is stopped by the natural-stop control including no
braking process. Note that, when the operating mode is switched
while the ON-lock control is performed, the motor 30 is stopped by
the active-stop control including the braking process as described
above. Namely, the stop control performed by the controller 106
includes at least two stop controls (active-stop control and
natural-stop control) with different braking forces to the motor
30, and the controller 106 performs either of these two stop
controls in accordance with a predetermined condition.
[0059] As described above, when the hammer mode is selected, the
motor 30 can be started up and the ON-lock control can be performed
by one operation of the ON-lock button 80. In other words, the
ON-lock control can be performed only when the hammer mode is
selected. In addition, lighting of the LED contained in the ON-lock
button 80 (FIGS. 1 and 2) notifies that the ON-lock control is
performed. Moreover, when the operating mode is switched while the
ON-lock control is performed, the active-stop control including the
braking process is performed. This avoids the occurrence of
reaction due to sudden transmission of a rotational force. On the
other hand, when the trigger lever 70 or the ON-lock button 80
(FIGS. 1 and 2) is operated while the ON-lock control is performed,
the natural-stop control including no braking process is performed.
In other words, the operation of the trigger lever 70 or the
ON-lock button 80 can stop the ON-lock control, and thus stop the
motor 30. Consequently, even when the trigger lever 70 and the
ON-lock button 80 are operated again immediately after releasing
the operation thereof, the rotation number of the motor 30 smoothly
rises.
[0060] When the ON-lock signal is not received in the step S5 (S5:
No), the controller 106 determines whether the main switch 71 is
turned on or not (S15). Namely, the controller 106 determines
whether the trigger lever 70 (FIGS. 1 and 2) is pulled or not. When
the main switch 71 is turned on (S15: Yes), the controller 106
turns on the motor 30 (S16). After turning on the motor 30, the
controller 106 determines whether the main switch 71 is turned on
or not (S17), and when the main switch 71 is not turned on (S17:
No), the controller 106 stops the motor 30 by the natural-stop
control (S18). On the other hand, when the main switch 71 is turned
on (S17: Yes), the controller 106 determines the presence or
absence of the reception of the mode detection signal (S19).
Namely, the controller 106 determines the presence or absence of
the operation of the mode-switching dial 60 (FIGS. 1 and 2). When
it is determined, that the mode detection signal is received and
the mode is not switched (S19: No), the controller 106 returns to
the step S17. Thereafter, the controller 106 repeats the steps S17
and S19 to maintain the motor 30 in the operating state. However,
when it is determined that the mode detection signal is not
received and the mode is switched (S19: Yes) during the repetition
of the steps S17 and S19, the controller 106 stops the motor 30 by
the active-stop control (S20).
[0061] As described above, when the hammer mode is selected, the
motor 30 can be started up also by the operation of the trigger
lever 70 shown in FIGS. 1 and 2, and the motor 30 can be turned
on/off based on the operation of the trigger lever 70. At this
time, the natural-stop control including no braking process is
performed when the operation of the trigger lever released during
the rotation of the motor 30, and the active-stop control including
the braking process is performed when the operating mode is
switched. In the former case, even when the trigger lever 70 is
operated again immediately after releasing the operation of the
trigger lever 70, the rotation number of the motor 30 smoothly
rises. In the latter case, it is possible to avoid the occurrence
of reaction due to sudden transmission of a rotational force caused
by the mode switching.
[0062] The present invention is not limited to the above-described
embodiment, and various modifications and alterations can be made
within the scope of the present invention. For example, the present
invention is applicable also to an impact tool in which a
rotational movement of a motor is converted into a reciprocating
motion of a piston through a reciprocating-type conversion
mechanism. In addition, the first operating mode in the present
invention includes an operating mode in which only an impact force
is transmitted to a tool bit, and the second operating mode
includes an operating mode in which a rotational force is
transmitted to the tool bit. Although the hammer drill according to
the above-described embodiment is the impact tool having operating
modes such as the hammer mode and the hammer drill mode, the impact
tool of the present invention includes an impact tool having
operating modes such as a hammer mode and a drill mode and an
impact tool having three operating modes such as a hammer mode, a
drill mode, and a hammer drill mode.
[0063] Note that the natural-stop control including no braking
process that actively stops the rotation of the motor is one
example of the stop control with a smaller braking force than that
of the active-stop control. In other words, the natural-stop
control and the active-stop control are one example of two stop
controls with different braking forces.
[0064] The present invention includes an embodiment in which an
active-stop control having a relatively small braking force and an
active-stop control having a relatively large braking force are
selectively performed in accordance with a predetermined condition,
and further includes an embodiment in which a controller controls
ON/OFF of switching elements to control the number of closed
circuits of oils and the formation time of the closed circuit,
thereby changing a braking force in accordance with an operating
mode. Furthermore, the present invention includes not only an
embodiment in which the braking force in the active-stop control is
constant, but also an embodiment in which the braking force
varies.
REFERENCE SIGNS LIST
[0065] 1 hammer drill [0066] 2 cylinder housing [0067] 3
intermediate housing [0068] 4 motor housing [0069] 5 handle [0070]
10 cylinder [0071] 20 piston [0072] 30 brushless motor (motor)
[0073] 60 mode-switching dial [0074] 62 sensor [0075] 70 trigger
lever [0076] 71 main switch [0077] 80 ON-lock button
* * * * *